System and method for providing substantially uninterrupted digital video during a switching event between a first digital video source and a second digital video source

ABSTRACT

When switching sources, resolutions or refresh rates in a video distribution network, switching times are reduced by maintaining video lock and security authentication between a video switcher and a video sink. The scaler maintains video lock and security authentication by continuing to generate video timing data during switching events. The scaler also facilitates an aesthetically pleasing transition by generating image content data prior to and after the switching event.

PRIORITY INFORMATION

The present application claims priority under 35 U.S.C. §120 to U.S.Non-Provisional patent application Ser. No. 13/764,315, filed 11 Feb.2013, and which itself claims priority to U.S. Provisional PatentApplication Ser. No. 61/597,448, filed 10 Feb. 2012, the entire contentsof all of which are expressly incorporated herein by reference.

CROSS REFERENCE TO RELATED APPLICATIONS

Related subject matter is disclosed in the following U.S. patent andco-pending U.S. Non-provisional patent applications, the entire contentsof all of which are expressly incorporated herein by reference: U.S.Non-provisional patent application Ser. No. 14/500,938, filed 29 Sep.2014, now U.S. Pat. No. 9,456,236 (Attorney Docket No. CP00190-02); U.S.Non-provisional patent application Ser. No. 15/272,787, filed 22 Sep.2016 (Attorney Docket No. CP00190-03); and U.S. Non-provisional patentapplication Ser. No. 15/272,810, filed 22 Sep. 2016 (Attorney Docket No.CP00190-04).

BACKGROUND

Technical Field

Aspects of the embodiments relate generally to video distributionnetworks. More particularly, aspects of the embodiments relate tosystems and methods for distributing video protected by a digital rightsmanagement scheme following switching events between different digitalvideo sources.

Background Art

Video distribution networks are increasingly common installations incommercial and residential facilities. Components of a videodistribution network are typically located throughout the facility andnetworked allowing video to be distributed from one or more video sourceto one or more video sinks. For example, a typical video distributionnetwork in a home may comprise a multitude of video sources, such asBlu-Ray Disc Players, media servers, digital video disc (DVD) players,Digital Video Recorders (DVR), and cable boxes. These video sources maybe centrally located such as in an equipment rack in a closet anddistributed via a chain of switches and repeaters to various videosinks, such as television displays, computer monitors and projectors,throughout the home.

However, as the digital distribution of television, movies, and musicexpands, content providers are growing increasingly concerned about thesimplicity with which content pirates can copy and share copyrightedmaterial. Various digital rights management (DRM) schemes have beendeveloped to ensure that television shows, movies and music can only beviewed or heard by authorized parties (i.e. paying customers). One DRMscheme to protect digital content as it is transmitted over cablesbetween devices is known as High-Bandwidth Digital Content Protection(HDCP). HDCP is a specified method developed by Digital ContentProtection, L.L.C. (DCP) for protecting copyrighted digital content asit travels across connection interfaces and protocols such asDisplayPort (DP), Digital Video Interface (DVI), High-DefinitionMultimedia Interface (HDMI). The HDMI specification defines an interfacefor carrying digital audiovisual content from a source such as a Blu-RayDisc player, to a sink or display device such as a television (TV).

There are three facets to HDCP. First, there is the authenticationprotocol, through which a source verifies that a given sink is licensedto receive HDCP content. With the legitimacy of the sink determined,encrypted HDCP content may be transmitted between the two devices, basedon shared secrets established during the authentication protocol. Theuse of such shared secrets prevents eavesdropping devices from utilizingthe content. Finally, in the event that legitimate devices arecompromised to permit unauthorized use of HDCP content, renewabilityallows a source to identify such compromised devices and prevent thetransmission of HDCP content.

The HDCP authentication protocol is an exchange between an HDCPcompliant source and an HDCP compliant sink that affirms to the sourcethat the sink is authorized to receive HDCP content by demonstratingknowledge of a set of secret device keys by transmitting a key selectionvector (KSV). Each HDCP device is provided with a unique set of thesesecret device keys, referred to as the Device Private Keys, from DCP.The communication exchange also provides for both the HDCP compliantsource and sink to generate a shared secret value that cannot bedetermined by eavesdropping on that exchange. By having that sharedsecret information embedded into the demonstration of authorization, theshared secret can then be used as a symmetric key to encrypt HDCPcontent intended only for the authorized device. Thus, a communicationpath is established between the HDCP source and HDCP sink that onlyauthorized devices can access.

In order for an HDCP compliant source to successfully transmit protectedcontent to one or more HDCP compliant sinks through an HDCP compliantrepeater, a more involved authentication process must first occur. Toaffirm the downstream sinks to the upstream sources, the HDCP repeatermust pass along the KSVs of each downstream receiver to the upstreamsource. The HDCP source checks these KSVs against an HDCP RevocationList maintained by DCP, LLC (“HDCP blacklist”) in order to determine ifeach of the downstream sinks are licensed to receive the protectedcontent. If all the downstream sinks are determined to be licensed toreceive the protected content, the upstream source transmits theprotected content to the HDCP repeater. It is the responsibility of theHDCP repeater to then establish and periodically manage authenticatedlinks with each of its connected HDCP receivers.

While HDCP offers the benefit of encrypted content transmission, therequired authentication protocol increases the switching delay in videodistribution networks. Each time a new path for video distribution isdesired, the links forming those paths must be authenticated. Forexample, when a user desires to switch to a different video source, notonly must the new video source authenticate with the repeater, but therepeater must also re-authenticate with the video sink. Increasedswitching times are disrupting and bothersome to users. In complex videodistribution systems with multiple layers, this problem is even moreamplified. Additionally, because HDCP scheme operates under the surface,most users do not realize that the increased time is the result of copyprotection schemes and often unfairly attribute them to the individualcomponents in the video distribution network.

An additional factor in the high switching delay in video distributionunits, is caused by the need for processing in video distributionnetworks. Scalers are employed to change the resolution or refresh rateof distributed video and are common components in video distributionnetworks, either as separate components or integrated into othercomponents in the network. Each time a video scaler receives audiovisualdata at a new resolution, there is a delay before the scaler outputs anynew video. The video scaler must load data and format before outputtingscaled video. This is known as achieving video lock. During a switchingevent, each scaler in the distribution path must achieve video lock insuccession. In complex video distribution systems with multiple layers,this delay is amplified.

Additionally, dependent on the characteristics of the display, viewersmay be subjected to disrupting video artifacts or snow during switches.Manufacturers handle disrupted video in different ways. Some displaysmay show “snow” when video is disrupted. Other may display pixilatedimages or ghost images. Many viewers find these display responsesdisturbing and lead some to believe that there is a problem with theirequipment when no such problem exists. Users may experience theauthentication process as a delayed period with snow or disorientingvideo artifacts.

There are certain problems, therefore, with the conventional systems,solutions, devices described above for viewing video when switchingoccurs. Accordingly, it would be desirable to provide methods, modes,and systems for distributing video protected by a digital rightsmanagement scheme following switching events between different digitalvideo sources.

SUMMARY

It is to be understood that both the general and detailed descriptionsthat follow are exemplary and explanatory only and are not restrictiveof the aspects of the embodiments.

Principles of the aspects of the embodiments provide a device and methodfor reducing the switching time of a video distribution network bymaintaining an authenticated security protocol link on a downstreamconnection of a switcher device. For example, according to an aspect ofthe embodiments, a switcher device comprises at least two input boards,a multiplexer and an output board. Each of the at least two input boardsare adapted to receive audiovisual data from a video source over asecurity protocol link. The multiplexer can be communicatively coupledbetween the at least two input boards and a transmitter board andadapted to dynamically route audiovisual data from the at least inputboards to the transmitter board. The output board can be adapted totransmit audiovisual data to a video sink over a security protocol linkand maintain the security protocol link as authentic.

According to a second aspect of the embodiments, a switcher devicecomprises at least two input boards, a multiplexer board and an outputboard. Each of the at least two input boards can be adapted to receiveaudiovisual data from a video source over an HDCP link. The multiplexerboard comprises a multiplexer communicatively coupled between the atleast two input boards and an output board and adapted to dynamicallyroute audiovisual data from the at least two input boards to the outputboard and a processing unit in communication with the multiplexer andthe output board and configured for transmitting a switch signal to themultiplexer and a prepare signal to the transmitter board prior to aswitching event. The output board can be adapted to transmit audiovisualdata to a video sink over and HDCP link, and comprises a receiveradapted to receive audiovisual data routed from the multiplexer, ascaler adapted to convert audiovisual data received via the multiplexerto video to a native resolution of the video sink, generate video timingdata at the native resolution of the video sink during the switchingevent and generate image content data for a period of time untilachieving video lock in response to receiving the prepare signal, and atransmitter adapted to encrypt and transmit generated audiovisual datato the video sink over an HDCP interface and maintain an authenticatedinterface with the video sink by outputting continuous audiovisual dataduring the switching event.

According to a second aspect of the embodiments, an output board for aswitcher device can be adapted to transmit audiovisual data to a videosink over a security protocol link. The output board comprises areceiver, a scaler and a transmitter. The receiver can be adapted toreceive audiovisual data. The scaler can be adapted to convert theaudiovisual data to a native resolution of the video sink and adapted togenerate audiovisual data during a switching event. The transmitter canbe adapted to encrypt and transmit encrypting and transmitting theoutput of the scaler, and is further adapted to maintain anauthenticated interface with the video sink.

According to further aspects of the embodiments, a method for reducingswitching delay when switching sources in a video distribution networkcomprises receiving audiovisual data at a first input board from a firstvideo sink over a security protocol link, routing audiovisual data fromthe first input board to an output board, transmitting audiovisual datafrom the output board to a video sink over a security protocol link,receiving a user control signal to switch to a second video source,generating video timing data at the output board during a delay betweenreceiving audiovisual data from the first input board and receivingaudiovisual data from the second input board to maintain authenticity ofsecurity protocol link between the output board and the video sink,receiving audiovisual data at a second input board from a second videosink over a security protocol link, routing audiovisual data from thesecond input board to the output board; and transmitting audiovisualdata from the output board to the video sink over a security protocollink.

According to still further aspects of the embodiments, a computerprogram product for reducing the switching time in a video distributionnetwork is provided, the computer program product comprising a computerreadable storage medium having computer readable code embodiedtherewith. The computer readable program code comprises computerreadable program code adapted to detect a user control signal to switchfrom a first video source to a second video source, transmit a preparesignal to a processing unit of an output board in response to thedetection of the user control signal, detect the prepare signal,instruct a scaler to generate audiovisual data in response to thedetection of the prepare signal, cease routing audiovisual data from afirst video source to the output board, continue generating video timingdata at the scaler of the output board, begin routing audiovisual datafrom a second video source to the input board, cease generating imagecontent data upon achieving video lock.

Aspects of the embodiments are directed to overcome or at leastameliorate one or more of several problems, including but not limitedto: reducing the switching delay of a video distribution networktransmitting protected video.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying figures further illustrate aspects of the embodiments.

The components in the drawings are not necessarily drawn to scale,emphasis instead being placed upon clearly illustrating principles ofaspects of the embodiments. In the drawings, like reference numeralsdesignate corresponding parts throughout the several views.

FIG. 1 is a block diagram of a High-Bandwidth Digital Content Protection(HDCP) system according to aspects of the embodiments.

FIG. 2 is a block diagram of an HDCP system wherein two or more HDCPdevices are interconnected through at least one HDCP-protected Interfaceaccording to aspects of the embodiments.

FIG. 3 is a block diagram of a switcher device according to aspects ofthe embodiments.

FIG. 4 is a block diagram of the switcher device shown in FIG. 3,according to aspects of the embodiments.

FIG. 5 shows a video distribution network, according to aspects of theembodiments.

FIG. 6 is a block diagram of the output board shown in FIG. 5, accordingto aspects of the embodiments.

FIG. 7 is a flowchart of a method for reducing the switching time in avideo distribution network, according to aspects of the embodiments.

DETAILED DESCRIPTION

List of Reference Numbers for the Major Elements in the Drawing

The following is a list of the major elements in the drawings innumerical order.

-   -   100 High Bandwidth Digital Content Protection System    -   102 Interface Cable or Link    -   104 Audio/Video Source    -   106 Audio Video Sink    -   108 Secret Device Keys    -   200 High Bandwidth Digital Content Protection System    -   202 HDCP Content (Audiovisual Data)    -   210 Control Function    -   212, 215 HDCP Transmitter    -   214, 216 HDCP Receiver    -   219 Repeater    -   220 Central Processing Unit    -   300 Video Distribution Network    -   302 Switcher Device    -   304 Control Signal    -   306 Multiplexer    -   308 Input board    -   310 Output board    -   316 User Control Signal    -   318 Switcher Processing Unit    -   320 Transceiver    -   322 Control System    -   323 User Interface Device (e.g., Wireless/Mobile Device)    -   324 User Interface Device    -   401 Receiver    -   402 Output Scaler    -   403 Output Processing Unit    -   502 Interface Cable (Link)    -   508 Extended Reception Board    -   510 Extended Transmission Board    -   601 Receiver    -   615 HDCP Transmitter    -   700 Method for Reducing Switching Time in a Video Distribution        Network    -   701-714 Steps of Method 700

LIST OF ACRONYMS USED IN THE SPECIFICATION

The following is a list of the acronyms used in the specification inalphabetical order.

-   -   AV Audiovisual    -   CAT5e Category 5 Enhanced    -   DC Direct Current    -   DCP Digital Content Protection, LLC    -   DDC Display Data Channel    -   DM DigitalMedia    -   DRM Digital Rights Management    -   DVD Digital Video Disc    -   DVR Digital Video Recorder    -   EDID Extended Display Data Channel    -   HDCP High-Definition    -   HDMI High-Definition Multimedia Interface    -   PCB Printed Circuit Board    -   STP Shielded Twisted Pair    -   TMDS Transition Minimized Differential Signaling    -   UTP Unshielded Twisted Pair

Authorized device—An HDCP device that is permitted access to HDCPcontent. An HDCP transmitter may test if an attached HDCP receiver is anauthorized device by successfully completing the first and, whenapplicable, second part of the authentication protocol. If theauthentication protocol successfully results in establishingauthentication, then the other device is considered by the HDCPtransmitter to be an authorized device.

Downstream—Term used as an adjective to refer to being towards thesink/display of the HDCP content stream.

DVI—Short for Digital Video (or Visual) Interface, a digital interfacestandard created by the Digital Display Working Group (DDWG) toaccommodate both analog and digital monitors.

HDCP—short for High-Bandwidth Digital Content Protection, a specifiedmethod developed by Digital Content Protection, L.L.C. (DCP) forprotecting copyrighted digital content as it travels across connectioninterfaces and protocols such as DisplayPort (DP), Digital VideoInterface (DVI), High-Definition Multimedia Interface (HDMI).

HDCP content—consists of audiovisual content that is protected by theHDCP system. HDCP content includes the audiovisual content in encryptedform as it is transferred from an HDCP transmitter to an HDCP receiverover an HDCP-protected Interface.

HDCP device—Any device that contains one or more HDCP-protectedinterface ports and is designed in adherence to HDCP.

HDCP Encryption—The encryption technology of HDCP when applied to theprotection of HDCP content in an HDCP system.

HDCP-protected Interface—An interface for which HDCP applies.

HDCP-protected Interface Port—A connection point on an HDCP Device thatsupports an HDCP-protected Interface.

HDCP receiver—An HDCP device that can receive and decrypt HDCP contentthrough one or more of its HDCP-protected interface ports.

HDCP repeater—An HDCP device that can receive and decrypt HDCP contentthrough one or more of its HDCP-protected interface ports, and can alsore-encrypt and emit the HDCP content through one or more of itsHDCP-protected interface ports. An HDCP repeater may also be referred toas either an HDCP receiver or an HDCP transmitter when referring toeither the upstream side or the downstream side, respectively.

HDCP transmitter—An HDCP device that can encrypt and emit HDCP contentthrough one or more of its HDCP-protected interface ports.

HDMI—Short for High-Definition Multimedia Interface, anindustry-supported, uncompressed, all-digital audio/video interface.

Upstream—Term used as an adjective to refer to being towards the sourceof the HDCP content stream. The antonym of “downstream,” defined above.

FIGS. 1 and 2 illustrate examples of High-Bandwidth Digital ContentProtection (HDCP) systems 100, 200 according to aspects of theembodiments. Referring to FIG. 1, HDCP system 100 encrypts the digitalcontent transmission between video source 104 (set-top box, computer,DVD, among other type of devices) and sink or display 106 (LiquidCrystal Display, television, among other types of devices) via interface102 such as a Digital Video Interface (DVI), a High-DefinitionMultimedia Interface (HDMI), and a DisplayPort interface.

FIG. 2 illustrates an HDCP system 200 wherein two or more HDCP devices104, 106 are interconnected through an HDCP repeater and twoHDCP-protected Interfaces 102 a, 102 b (collectively 102), according toaspects of the embodiments. Each point-to-point HDCP link involves oneHDCP transmitter 212, and one HDCP receiver 214. As such, the HDCPrepeater 219 can decrypt the HDCP content at the HDCP receiver 216 oneach of its inputs. The repeater 219 can then re-encrypt the data withan HDCP transmitter 215 on each of its outputs. The repeater 219 caninform the upstream device of its downstream connection, but generallyrepeater 219 maintains those connections. The audiovisual contentprotected by HDCP, HDCP content 202, flows from an upstream contentcontrol function 210 into HDCP system 200 at the most upstreamtransmitter 212. From there, HDCP content 202, encrypted by HDCP system200, flows through a tree-shaped topology of HDCP receivers 214 overHDCP-protected Interfaces 102. Before sending data, each transmitter212, 215 checks that the HDCP receivers 214, 216 are authorized toreceive HDCP content 202. If so, transmitter 212 encrypts HDCP content202 to prevent eavesdropping as it flows to receiver 216. Centralprocessing unit 220 includes firmware to process HDCP content 202 andother information and control.

Device manufacturers typically buy HDCP chips from a DCP-licensedsilicon vendor. These chips usually also provides transition minimizeddifferential signaling (TMDS) encoders or decoders and otherHDMI-specific features. Transmitters 212 can have at least one HDCPtransmitter chip and receivers 216 can have at least one HDCP receiverchip. HDCP transmitters 212, and receivers 216 frequently require amicroprocessor to implement the authentication state machines.Transmitters 212, 215 can be HDMI transmitters.

The Authentication and Encryption Protocols

HDCP authentication consists of three parts:

Part One: source 104 authenticates with sink/display 106 connected toits output. If successful, encryption is enabled and audiovisual (NV)content transmission begins.

Part Two: This part is used if the downstream device is repeater 219.Repeater 219 authenticates with the devices connected to its output(s)and passes the HDCP tree topology information up to source 104. Source104 is the root and sinks/display 106 are the leaves, while repeaters219 make up the branches of the tree.

Part Three: Source 104 performs periodic checks with sink/display 106 toensure that encryption is in sync. As mentioned above, repeater 219generally maintains its downstream connections. If any part ofauthentication fails or any revoked devices are found in the HDCP tree,transmitter 212 can stop sending protected content and authenticationstarts over at Part One.

Authentication Part One

Part One of authentication is a key exchange protocol. Transmitter 212and receiver 216 calculate a common secret session key 108 to be usedfor encryption. If they cannot come up with the same key value,authentication fails and receiver 216 will not be able to decrypt theHDCP content 202. The session key is derived from each device's privatekey according to the following protocol:

First transmitter 212 generates a random number “An” and sends it toreceiver 216. This value will be used later in the protocol. Devices104, 106 then exchange KSVs. Receiver 216 also sends its REPEATER bit, aflag that indicates whether or not it is part of a repeater. Now eachdevice 104, 106 has the other device's Key Selection Vector (KSV). Eachdevice 104, 106 uses the other device's Key Selection Vector to selecttwenty of its own keys. The forty bits in the KSV correspond to theindexes of each of the forty private keys. For every set bit in thereceived KSV, the local private key at that index is selected. All KSVshave twenty set bits, so twenty keys are selected. Devices 104, 106 theneach add up their selected keys to come up with the sums Km and Km′, forthe transmitter and receiver, respectively 212, 216. For authenticationto succeed, Km and Km′ must match. Each device 104, 106 tells the otherwhich of its own unique, secret keys to select, and they both come upwith the same sum. That may seem counter-intuitive, but it is theaforementioned mathematical relationship between the keys and the KSVsthat accounts for this behavior. Source 104 can then determine whetherKm and Km′ match. However, they are secret values, so they cannot betransmitted over interface cable 102 for the DDC. Each device 104,106feeds Km (or Km′), the random number “An”, and the REPEATER bit intotheir respective HDCP cipher engines in order for transmitter 212 toverify that the values match without sending them across cable 213 foreveryone to see. The resulting data stream is split into three values:

R0/R0′: This return value can be shared between the devices 104, 106 andis used to verify that authentication was successful.

Ks/Ks′: This value is kept private and is used as the encryption sessionkey for the HDCP cipher.

M0/M: This value is also kept private and is used in Part Two ofauthentication (if the downstream device is repeater 219).

Receiver 219 sends R0′ to transmitter 212, which compares it againstits' own R0 value. If they match, that proves that the sums Km and Km′matched, and authentication is successful. Furthermore, the session keysKs and K match, so the receiver 214 will be able to decrypt the contentencrypted by the transmitter. If Part One of authentication wassuccessful, the transmitter 212 may begin sending encrypted HDCP content202. If the downstream device is repeater 219, the repeater 219 mustauthenticate with its own downstream device according to the sameprotocol. Transmitter 212 then starts a 5-second timer to allow forrepeater 219 to perform Part Two of authentication. If Part Two fails ortimes out, authentication fails and transmitter 212 must stoptransmitting HDCP content 202.

Authentication Part Two

Part Two of authentication only occurs if the downstream device is arepeater 219. The purpose of Part Two is to inform source 104 of alldownstream devices and the HDCP tree depth. Source 104 uses thisinformation to ensure that the tree topology maximums have not beenexceeded and to ensure that none of the downstream devices have beenrevoked by DCP. Repeater 219 first assembles a list of the KSVs of alldownstream devices, as well as the device count and the tree depth.Repeater 219 then passes this information up to source 104. To ensurethat this information has not been tampered with during transmission,each device takes this list, appends its secret value M0/M0′ from PartOne, and calculates a SHA-1 hash of the whole thing. Transmitter 212reads the hash result from receiver 214 and compares it against its own.If they match, Part Two of authentication is successful.

Authentication Part Three

All HDCP devices are considered authenticated after successfulcompletion of Authentication Parts One and Two. Part Three is simply alink integrity check to ensure that encryption is in sync between alltransmitter/receiver pairs 212, 214, 215, 216 in the tree. To supportlink integrity checks, the return values Ri and Ri′ roll over to a newvalue every 128 frames. Recall that the initial Ri values R0 and R0′were generated during Part One of authentication. Every two seconds,transmitter 212 compares receiver's 216 Ri′ value against its own Rivalue to see if they match. If they do not, encryption is out of syncand receiver 216 cannot correctly decrypt HDCP content 202. The userwill see a scrambled or “snowy” image on the screen. In this casetransmitter 212 can then restart authentication from the beginning.

The three part authentication process increases switching delay whenswitching sources in a video distribution network. Switching delay isthe delay between switching an aspect of incoming audiovisual data to avideo sink, such as audiovisual data source, audiovisual data resolutionand audiovisual data refresh rate, and the incoming audiovisual databeing displayed on the video sink. Not only must devices authenticatethe HDCP link before video transmission, each time an upstream HDCP linkis switched, downstream HDCP links may be affected as well becauseaudiovisual data transmission to downstream links is interrupted. Eachtime video transmission is interrupted between an HDCP transmitter andan HDCP receiver, the HDCP link fails Part Three of the authenticationprocess and the authentication process must be restarted from Part One.This includes downstream connections that were previously authenticatedwith each other.

For example, in a video distribution network comprising a firstHDCP-compliant video source and a second HDCP compliant video sourceconnected to an HDCP compliant video sink via an HDCP compliant videoswitcher, when the video source transmitting HDCP content to the videosink is switched from the first video source to the second video source,not only must the second video source authenticate with the videoswitcher, but the downstream link between the video source and the videoswitcher must also be re-authenticated due to the disruption in videotransmission. This despite the fact that the HDCP link between the videosource and the video switcher was already authenticated. This issuebecomes increasingly burdensome in expansive video distribution networkswith many layers (i.e. a large tree topology).

Additionally, when video transmission is interrupted between an HDCPtransmitter and an HDCP receiver due to upstream switching and HDCPauthentication, any downstream video scalers must lock back on theincoming audiovisual data before outputting any scaled audiovisual data.This introduces delay in addition to the delay introduced by the HDCPauthentication process. For example, each time video transmission to asink is interrupted, video scaler internal to the sink will takeanywhere between two and ten seconds to lock onto the incomingaudiovisual data again. Those skilled in the art will recognize thatscaler operation is unpredictable and varies due to hardware andfirmware specification. Often, video scalers included in video sinks arenot optimized for reducing switching delay. Also unpredictable is videosink response while embedded video scalers achieve video lock. Presentedwith interrupted video, the video sink may display snow, pixilatedimages, video artifacts or a blank screen while internal scaler achievesvideo lock dependent on video sink manufacturer.

Because the HDCP authentication process operates in the background,often unknown to the user, long switching delays are unfairly blamed onvideo distribution components. Users may experience the authenticationprocess as a delayed period with snow or disorienting video artifacts.This could result in undeserved user dissatisfaction with themanufacturer of the components in the video distribution network.

As will be explained below, aspects of the embodiments disclose systems,apparatuses and methods for reducing the switching time in a videodistribution network. Aspects of the embodiments are directed towardsmaintaining authentication of downstream link during a switchingdiscontinuity, minimizing the interruption of video transmissionresulting from switching events. By outputting continuous video timingdata to a sink over a downstream HDCP link, even during switchingdiscontinuities, the downstream HDCP link satisfies the maintenancecheck in step three of HDCP authentication. Accordingly, steps one andtwo of the HDCP authentication protocol need not be repeated.Additionally, as a result of maintaining the authentication of the HDCPlink by outputting continuous video timing data during switchingdiscontinuities, video scalers downstream of the HDCP link (i.e.internal video sink scalers) will not lose video lock with the incomingvideo stream thereby reducing delay times further. Finally, byoutputting black frames of image data, the content displayed duringswitching events is controlled.

FIG. 3 is a block diagram of switcher device 302 adapted to reduceswitching time in a video distribution network according to aspects ofthe embodiments. Video distribution network 300 is an HDCP system andincludes at least one source 104 a, 104 b, . . . , 104 n (collectively104) and at least one sink or display 106 a, 106 b, . . . , 106 n(collectively 106). At least two sources 104 include HDCP transmitter212, such as an HDMI transmitter, adapted to transmit audiovisual datacomprising video timing data and image content data to at least one sink106. Each source 104 further includes a graphic generator (not shown) togenerate a graphic or image. HDCP transmitter 212 receives HDCP content202 from upstream content control function 210.

At least one sink includes an HDCP receiver, such as an HDMI receiver.Source 104 determines via the authentication process what content can beviewed, recorded, and shared based on sinks/displays 106 that supportHDCP and sinks/displays 106 that does not support HDCP. The output ofsource 104 is connected to input board 308 for switcher device 302through their HDCP-protected interfaces 304 and switcher device 302serves as an HDCP repeater for HDCP compliant content. Output board 310for switcher device 302 is connected to the input of sink/display 106via another interface 102 b. Interfaces 102 a, 102 b for the input boardand the output board of switcher device 302 may be an HDMI cable thatcarries a variety of signals such as one or more transition minimizeddifferential signaling (TDMS) data signals, digital display channel(DDC), hot plug detect (HPD), and RxSense. As will be described later,interfaces 102 a, 102 b for the input board and output board of switcherdevice 302 may also be a combination of one or more shielded twistedpairs (STP) and one or more unshielded twisted pairs (UTP), such asDigitalMedia (DM) cable available from Crestron Electronics, Inc. ofRockleigh, N.J.

When HDCP source 104 (more specifically source 104 a) detects an RxSensesignal from HDCP compliant sink/display 106 (more specificallysink/display 106 a), source 104 a will transmit HDCP content 202 tosink/display 106 a after the authentication process is successful.

HDCP content 202 is encoded into three data channels. These channels anda TMDS clock are carried over four differential pairs from source 104 tosink/display 106. The DDC is a communications interface similar to I2C.This interface provides two-way communication in a master-slaverelationship. Upstream device 104 is the DDC master and downstreamdevice 106 is the DDC slave. HDCP receiver 214 indicates its presence toHDCP transmitter 212 with the HPD signal. HDCP transmitter 212 is theHDCP Device most upstream, and receives HDCP content 202 from upstreamcontent control function 210.

Switcher device 302, functioning as an HDCP repeater, is a fully modularand expandable matrix switcher offering low-latency digital video andaudio switching, and HD lossless multi-room signal distribution, for alltypes of A/V sources. Switcher device 302 may be a Crestron DigitalMedia Switcher available from Crestron Electronics, Inc. of Rockleigh,N.J.

The Crestron Digital Media Switcher is field-configurable to handle, butnot limited to, eight, sixteen, and thirty-two audiovisual sources ofvirtually any type via input boards. The outputs are alsofield-configurable to provide, but not limited to, eight, sixteen, andthirty-two room outputs and/or HDMI outputs in a single chassis. Thechassis comprises slots for the insertion of input and output boards. Aswill be described later, the input boards and output boards may be inputboards and output boards, respectively, of the switcher device 302.Additionally, the input boards and output boards may operate external ofthe chassis of the Digital Media Switcher and be coupled to the DigitalMedia Switcher via intermediate cards inserted into slots in thechassis.

Switcher device 302 includes multiplexer 306 coupled in-between the atleast one input board 308 a, 308 b, 308 n (collectively 308) and atleast one output board 310 a, 310 b, 310 n (collectively 310).Multiplexer 306 may be, but is not limited to, a mechanical switch,electrically operated switch, solid state relay, latching relay, reedrelay, single pole single throw (SPST) relay, single pole double throw(SPDT) relay, double pole single throw (DPST) relay, and double poledouble throw (DPDT) relay.

Multiplexer 306 transmits HDCP content 202 from one of the at least twoinput boards 308 to first output board 310 a. Multiplexer 306dynamically switches between first input board 308 a and at least secondinput board 308 b based on user control signal 316 that selects eitherfirst video source 104 a or second video source 104 b to be displayed onvideo sink 106 a. Output board 310 can be coupled to the at least onesink/display 106 via interface cable 102 b. Interface cable 102 b can bean HDMI cable. Switcher 302 further includes processing unit 318 coupledto multiplexer 306. Processing unit 318 includes at least onetransceiver 320 for bidirectional communications with end user device(e.g. 324, 326), in part, to receive user control signal 316. End userdevice 324, 326 transmits user control signal 316 from touch paneldisplay 324 via control system 322. An end user may also transmit usercontrol signal 316 from wireless device 326. Software tools 328 can beloaded onto the wireless device and/or touch panel 324 to assist the enduser in selecting desired source 104 and sink 106. In response to theuser selecting desired source 104 for sink 106, the end user devicetransmits user control signal 316 to switcher device 302.

Upon the user selecting the desired source 104 for the at least onedesired display 106, source 104 can authenticate with switcher device302 as described above. Switcher device 302 can authenticate with the atleast one desired downstream sinks 106 as described above. Once theauthentication is complete, source 104 can transmit the HDCP content(i.e. HDCP protected audiovisual data) via the HDCP link between thesource and the repeater. This HDCP link comprises HDCP transmitter 212of the source, an HDCP interface, and HDCP receiver 214 of first inputboard 308 a. The HDCP receiver of input board 308 a receives the HDCPcontent and provides the audiovisual data unencrypted to multiplexer306. Multiplexer 306, dependent on user control signal 316 routes theunencrypted audiovisual data to the desired output board 310. Outputboard 310 processes and encrypts the audiovisual data and then transmitsthe HDCP content to the desired sink 106 over an HDCP link betweenoutput board 310 and video sink 106. The HDCP link between output board310 and video sink 106 comprises HDCP transmitter 215 of the outputboard, HDCP interface and HDCP receiver of the video sink.

Multiplexer 306 can be adapted to dynamically route the audiovisual dataaccording to the user control signal received at processing unit 318.For example, a user viewing content from first source 104 a, such as acable tuner, may desire to switch to second source 104 b, such as aBlu-ray disc player. When multiplexer 306 switches from routingaudiovisual data from the first source to routing audiovisual data fromsecond source 104 b, output board 310 experiences a switching delay as aresult of the delay caused by upstream HDCP authentication andmultiplexer 306 operation. A similar switching discontinuity may alsoresult from a change in resolution or change in refresh rate of thereceived audiovisual data.

Output board 310 of switcher device 302 according to aspects of theembodiments can be adapted to continuously output audiovisual dataincluding video timing data and image content data during switchingdiscontinuities such that the HDCP link between output board 310 andvideo sink 106 remains authenticated during the switch and anaesthetically pleasing display is shown during said switch. For example,output board 310 can output black frames of audiovisual data duringswitching discontinuities. Switching delay in video distribution network300 is minimized by maintaining the authentication of the HDCP link bycontinuously outputting video timing data. Additionally, by continuouslyoutputting video timing data to the video sink during switchingdiscontinuities, video lock is maintained in video processing devices,such as scalers, downstream from output board 310 (i.e. scalers internalto video sink), thereby further minimizing switching delay.

FIG. 4 is a block diagram of a portion of switcher device 302 shown inFIG. 3 according to aspects of the embodiments. Output board 310 afurther comprises receiver 401, output scaler 402, output processingunit 403 and HDCP transmitter 215. Receiver 401 can be adapted toreceive audiovisual data routed from first input board 308 a or secondinput board 308 b via multiplexer 306. As described below, according toaspects of the embodiments, receiver 401 can be an HDCP receiver adaptedto receive HDCP encrypted content.

Output scaler 402 receives the audiovisual data from receiver 401 andcan be adapted to convert the received audiovisual data to a nativeresolution of video sink 106. Output board 310 can receive the nativeresolution of video sink 106 via an EDID channel. Those skilled in theart will recognize that the operation of video scalers embedded in enduser devices are idiosyncratic depending on manufacturer and may performsubstantially below par, resulting in poor video quality and delayedperformance. Advantageously, by converting to the native resolution ofvideo sink 106, video processing is minimized in downstream embeddedvideo scalers.

According to aspects of the embodiments, output scaler 402 of outputboard 310 can be adapted to operate in a pass through mode in which theoutput scaler detects the resolution of the incoming audiovisual datavia the video timing data. The output scaler passes the incomingaudiovisual data through to the HDCP transmitter if the audiovisual datais routed to the output board already at a native resolution of thevideo sink.

Output scaler 402 can be further adapted to generate audiovisual datacomprising video timing data and image content data during switchingdiscontinuities. For example, during a switching discontinuity betweenreceiving audiovisual data from first source 104 a and audiovisual datafrom second source 104 b, output scaler 402 can output black frames. Byoutputting a continuous stream of audiovisual data, more specificallyvideo timing data, to HDCP transmitter 215, the HDCP link between outputboard 310 and the source is maintained as authenticated during theswitch. In addition, by outputting black frames of audiovisual data,more specifically image content data, the end user experiences a cleantransition from first source 104 a to second source 104 b. In otheraspects of the embodiments, output scaler 402 can generate frames ofimage content data of a color other than black or may generate imagecontent data comprising an image, such as a corporate logo.

Prior to outputting audiovisual data from second source 104 b, outputscaler 402 can wait until it receives a sufficient amount of audiovisualdata from second source 104 b. This is known as achieving video lock.Following a switching discontinuity, output scaler 402 is furtherconfigured to generate image content data until video lock is achieved.By generating image content data until output scaler 402 achieves videolock, the user is presented with a clean transition during switchingevents.

Output scaler 402 can be adapted to operate in a free run mode byautomatically generating video timing data during switchingdiscontinuities.

Output scaler 402 can be further adapted to generate image content datain response to control signals from output processing unit 403. Uponreceiving the user control signal to switch the source of audiovisualdata and prior to transmitting a switching signal to multiplexer 306,switcher processing unit 318 transmits a prepare signal to outputprocessing unit 403. Output processing unit 403 in turn instructs outputscaler 402 to generate black frames of audiovisual data.

HDCP transmitter 215, such as an HDMI transmitter, converts and encodesthe audiovisual data output from output scaler 402 to one or more TDMSsignals for transmission to video sink 106 over the HDCP interface.According to aspects of the embodiments, the HDMI transmitter comprisesan HDCP transmitter chip and can further comprise TMDS encoders ordecoders and other HDMI-specific features. The audiovisual data isre-encrypted in accordance with the shared secret from authenticationbetween the HCDP repeater and the HDCP sink. HDCP transmitter 215receives the native resolution and the native refresh of the sink via aDisplay Data Channel (DDC) of the interface. The HDCP interface betweentransmitter and the HDCP receiver may be HDMI.

FIG. 5 shows switcher device 302 in a video distribution network 300,according to further aspects of the embodiments in which output board310 is contained in a housing external to switcher device 302. Videodistribution network 300 comprises extended transmission board 510coupled between the multiplexer 306 and output board 310. Videodistribution network 300 further comprises extended reception board 508.According to aspects of the embodiments, the extended reception board508 and extended transmission board 510 can be modular input and outputboards, respectively, configured to be inserted into switcher device302. As described below, the extended transmission and reception boardsallow for extended cable lengths that increases the functionality ofvideo distribution network 300. For example, output board 310 can becollocated in the same area as its corresponding video sink 106.Switcher device 302 can be remotely located in a central location or outof view, such as in an equipment closet. Similarly, first input board308 a and second input board 308 b may be collocated with first videosource 104 a and second video source 104 b, respectively.

According to aspects of the embodiments, output board 310 can be adaptedto receive encrypted audiovisual data via an HDCP link. Extendedtransmission board 510 is communicatively coupled between multiplexer306 and output board 310, and is further adapted to encrypt theaudiovisual data routed by multiplexer 306, and transmitting theencrypted audiovisual data to the output board 310 via an HDCP link. TheHDCP link comprises HDCP transmitter 615 of extended transmission board510, HDCP interface 502, and HDCP receiver 401 of output board 310. HDCPinterface 502 can be made of one or more pairs of twisted cable or fiberoptical cable, such as DigitalMedia cable available from CrestronElectronics, Inc. of Rockleigh N.J. Those skilled in the art willrecognize that DigitalMedia cable is a multi-generational family ofinterface cables particularly designed for media transmission forextended lengths.

Within a single plenum-rated jacket, original DigitalMedia cablecontains one high-bandwidth/low-crosstalk shielded 4-twisted pair (STP)cable, one CAT5e unshielded 4-twisted pair (UTP) cable, and one DMNetcable. The STP “Audiovisual data” cable is of a specialized constructiondesigned to allow the longest possible cable lengths for transportinghigh-definition digital video and audio. The Cat5e “Data Management”cable carries high-speed Ethernet and other data, plus 5V direct current(DC) power. Finally, the DMNet cable carries additional proprietarycontrol signals and 24V DC power. Original DigitalMedia cable is ratedfor up to 220 ft of audiovisual transmission.

FIG. 6 is a block diagram of the extended transmission board and theoutput board shown in FIG. 5, according to aspects of the embodiments.The block diagram of output board 310 in FIG. 5 is similar to the blockdiagram of output board 310 in FIG. 4, with the exception being that inFIG. 5, receiver 401 is an HDCP receiver adapted to receive HDCP contentover HDCP interface 502. Extended transmission board 510 comprisesreceiver 601 and HDCP transmitter 615.

FIG. 7 is a flowchart illustrating method 700 for reducing the switchingtime in a video distribution network 300, according to aspects of theembodiments.

In step 701, switcher device 302 receives audiovisual data at firstinput board 308 a via an HDCP link between first video sink 106 a andfirst input board 308 a.

In step 702, switcher device 302 routes audiovisual data from firstinput board 308 a to output board 310 a.

In step 704, output board 310 transmits audiovisual data to video sink106 over a security protocol link. According to aspects of theembodiments, output board 310 scales the audiovisual data received fromfirst input board 308 a to the native resolution of video sink 106 (step703) prior to transmitting to video sink 106.

In step 705, processing unit 318 of switcher device 302 receives acontrol signal to switch from routing audiovisual data from first inputboard 308 a to routing audiovisual data from second input board 308 b.

According to aspects of the embodiments, switching device processingunit 318 transmits a prepare signal to output board 310 a, indicatingthat there will be a switching discontinuity (step 706).

According to aspects of the embodiments, output board 310 a is adaptedto generate image content data, such as black frames of video, inresponse to receiving the prepare signal from the switching deviceprocessing unit 318 (step 707). Scaler 402 outputs the generated imagecontent data rather than the live image content data being routed tooutput board 310 a from multiplexer 306.

In step 708, multiplexer 306 ceases routing audiovisual data from firstinput board 308 a.

In step 709, output board 310 continues generating video timing data ata native resolution during the delay between receiving audiovisual datafrom first input board 308 a and receiving audiovisual data from secondinput board 308 b. By outputting a substantially continuous stream ofvideo timing data, output board 310 a maintains the authenticity of thesecurity link between output board 310 a and video sink 106.

In step 710, switcher device 302 receives audiovisual data at secondinput board 308 b via an HDCP link between second video sink 106 b andsecond input board 308 b.

In step 711, switcher device 302 routes audiovisual data from secondinput board 308 b to output board 310 a.

In step 712, output board 310 a continues generating and outputtingimage content data (i.e. black frames of video) until video lock isachieved.

In step 714, output board 310 a transmits live image content data routedfrom second input board 308 a to video sink 106 over an HDCP link.According to aspects of the embodiments, output board 310 a scales theaudiovisual data received from first input board 308 a to the nativeresolution of video sink 106 (step 713) prior to transmitting thereceived audiovisual data to video sink 106.

The following is a pseudo-code representation of the operation inaccordance with aspects of the embodiments.

(a) Detect a user control signal to switch from a first video source toa second video source;

(b) Transmit a prepare signal to a processing unit of an output board inresponse to the detection of the user control signal;

(c) Detect the prepare signal at the output board;

(d) Instruct scaler to generate image content data;

(e) Cease routing audiovisual data from a first video source to theoutput board;

(f) Continue generating video timing data at the scaler of the outputboard;

(g) Begin routing audiovisual data from a second video source to theinput board; and

(h) Cease generating image content data upon achieving video lock.

Any process descriptions or blocks in flow charts should be understoodas representing modules, segments or portions of code that include oneor more executable instructions for implementing specific logicfunctions or steps in the process. Alternate implementations can beincluded within the scope of the aspects of the embodiments in whichfunctions may be executed out of order from that shown or discussed,including substantial concurrence or reverse order, depending on thefunctionality involved, as would be understood by those reasonablyskilled in the aspects of the embodiments. Also, steps disclosed asseparate can be performed concurrently or combined, and a step shown asdiscrete can be performed as two or more steps. Furthermore, numericalvalues and disclosures of specific hardware are illustrative rather thanlimiting. Moreover, while aspects of the embodiments have been disclosedin the context of HDMI, aspects of the embodiments can be implementedfor use with another suitable interface that uses HDCP, such as DVI orany substantially HDMI-like interface. Therefore, aspects of theembodiments should be construed as limited by only the appended claims.

In this description, various functions and operations can be describedas being performed by or caused by software code to simplifydescription. However, those skilled in the art will recognize what ismeant by such expressions is that the functions result from execution ofthe code by a processor or processing unit, such as a microprocessor.Alternatively, or in combination, the functions and operations can beimplemented using special purpose circuitry, with or without softwareinstructions, such as using an application-specific integrated circuit(ASIC) or field-programmable gate array (FPGA). Embodiments can beimplemented using hardwired circuitry without software instructions, orin combination with software instructions. Thus, the techniques arelimited neither to any specific combination of hardware circuitry andsoftware, nor to any particular source for the instructions executed bythe data processing system.

While some embodiments can be implemented in fully functioning computersand computer systems, various embodiments are capable of beingdistributed as a computing product in a variety of forms and are capableof being applied regardless of the particular type of machine ofcomputer-readable media used to actually effect the distribution.

At least some aspects disclosed can be embodied, at least in part, insoftware. That is, the techniques may be carried out in a computersystem or other data processing system in response to itsprocessor/processing unit, such as a microprocessor, executing sequencesof instructions contained in a memory, such as ROM, volatile RAM,non-volatile memory, cache or a remote storage device.

Routines executed to implement the embodiments can be implemented aspart of an operating system, middleware, service delivery platform, SDK(software development kit) component, web services, or other specificapplication, component, program, object, module or sequence ofinstructions referred to as “computer programs”. Invocation interfacesto these routines can be exposed to a software development community asan API (application programming interface). The computer programstypically comprise one or more instructions set at various times invarious memory and storage devices in a computer, and that, when readand executed by one or more processors/processing units in a computer,cause the computer to perform operations necessary to execute elementsinvolving the various aspects.

A machine readable medium can be used to store software and data whichwhen executed by a data processing system causes the system to performvarious methods. The executable software and data can be stored invarious places, including for example ROM, volatile RAM, non-volatilememory and/or cache. Portions of this software and/or data can be storedin any of these storage devices. Further, the data and instructions canbe obtained from centralized servers or peer to peer networks. Differentportions of the data and instructions can be obtained from differentcentralized servers and/or peer-to-peer networks. Different portions ofthe data and instructions can be obtained from different communicationsessions or in a same communication session. The data and instructionscan be obtained in their entirety prior to the execution of theapplications. Alternatively, portions of the data and instructions canbe obtained dynamically, just in time, when needed for execution. Thus,it is not required that the data and instructions be on a machinereadable medium in entirety at a particular instance of time.

Examples of computer-readable media include, but are not limited to,recordable and non-recordable type media, such as volatile andnon-volatile memory devices, read-only memory (ROM), random accessmemory (RAM), flash memory devices, floppy and other removable disks,magnetic disk storage media, optical storage media (e.g. Compact DiscRead-Only Memory (CD ROM), Digital Versatile Discs (DVDs), etc.) amongothers. The instructions may be embodied in digital and analogcommunication links for electrical, optical, acoustical or other formsof propagated signals, such as carrier waves, infrared signals, digitalsignals, etc.

In general, a machine readable medium includes any mechanism thatprovides (i.e. stores and/or transmits) information in a form accessibleby a machine (e.g. a computer, network device, personal digitalassistant, manufacturing tool, any device with a set of one or moreprocessors, etc.).

In various embodiments, hardwired circuitry may be used in combinationwith software instructions to implement the techniques. Thus, thetechniques are neither limited to any specific combination or hardwarecircuitry and software nor to any particular source for the instructionsexecuted by the data processing system.

Although some of the drawings illustrate a number of operations in aparticular order, operations which are not order dependent may bereordered and other operations can be combined or broken out. While somereordering or other groupings are specifically mentioned, others will beapparent to those of ordinary skill in the art and so do not present anexhaustive list of alternatives. Moreover, it should be recognized thatthe stages could be implemented in hardware, firmware, software or anycombination thereof.

Although illustrative aspects of the embodiments have been describedherein with reference to the accompanying drawings, it is to beunderstood that the aspects of the embodiments are not limited to thoseprecise embodiments, and that various other changes and modificationsmay be made therein by one skilled in the art without departing from thescope of the appended claims.

INDUSTRIAL APPLICABILITY

To solve the aforementioned problems, aspects of the embodiments aredirected towards a unique device in which output board 310 with scaler402 minimizes switching delay in video distribution network 300 byoutputting a substantially continuous stream of audiovisual data duringswitching events.

ALTERNATE EMBODIMENTS

Alternate embodiments can be devised without departing from the spiritor the aspects of the embodiments. For example, during switching events,output scaler 402 can generate video information such that a switchinggraphic will be displayed on the screen or a color other than black.

What is claimed is:
 1. A digital video switcher device (switcher device)comprising: an output board; at least two input boards, each of the atleast two input boards adapted to receive digital audiovisual data froma digital video source over a security protocol link; and a multiplexercommunicatively coupled between the at least two input boards and theoutput board, and wherein the multiplexer is adapted to dynamicallyroute the digital audiovisual data from the at least two input boards tothe output board, and wherein the output board is adapted to generate acontinuous stream of uninterrupted digital video timing data in theabsence of digital video timing data received from either or both of theat least two input boards.
 2. The switcher device according to claim 1,wherein the output board is further adapted to transmit the digitalaudiovisual data to a downstream video sink over a security protocollink, and maintain the security protocol link in an authenticatedinterface with the downstream video sink during a switching eventbetween the at least two input boards by outputting a continuous streamof uninterrupted digital video timing data during the switching event.3. The switcher device according to claim 2, wherein the output boardcomprises: a scaler adapted to generate the continuous stream ofuninterrupted digital video timing data in the absence of digital videotiming data received from either or both of the at least two inputboards.
 4. The switcher device according to claim 3, wherein the outputboard comprises: a receiver adapted to receive the digital audiovisualdata routed from the multiplexer; a scaler adapted to convert thedigital audiovisual data received via the multiplexer to a nativeresolution of the digital video sink, generate a continuous stream ofuninterrupted video timing data during the switching event at the nativeresolution of the video sink during the switching event, and generateimage content data for a period of time until achieving video lock inresponse to receiving the prepare signal; and a transmitter adapted toencrypt and transmit digital audiovisual data to the digital video sinkover an HDCP interface and maintain the security protocol link in anauthenticated interface with the video sink by outputting the continuousstream of uninterrupted video timing data during the switching event. 5.The switching device according to claim 4, wherein the scaler is furtheradapted to operate in a free running mode by generating digital videotiming data during the switching event.
 6. The switcher device accordingto claim 3, wherein the scaler is further adapted to generate thecontinuous stream of uninterrupted digital video timing data in theabsence of digital video timing data received from either or both of theat least two input boards at a native resolution of the digital videosink.
 7. The switcher device according to claim 2 wherein the scaler isfurther adapted to generate black frames of digital image content dataduring the switching event.
 8. The switcher device according to claim 7wherein the scaler is further adapted to continue to generate blackframes of digital image content data until receiving a sufficient amountof digital image content data to generate a stable output of converteddigital image content data.
 9. The switcher device according to claim 2,wherein the security protocol comprises: High-Bandwidth Digital ContentProtection (HDCP).
 10. The switcher device according to claim 2 whereinthe switching event comprises: at least one of a switch from receivingfirst digital video from a first digital video source to receivingsecond digital video from a second digital video source, a switch fromreceiving digital video at a first resolution to receiving digital videoat a second resolution, and a switch from receiving digital video at afirst refresh rate to receiving digital video at a second refresh rate.11. The switcher device according to claim 1 further comprising: aprocessing unit in communication with the multiplexer and the outputboard and wherein the processing unit transmits a prepare signal to theoutput board a predetermined amount of time before transmitting a switchsignal to the multiplexer.
 12. An output board in a digital videoswitcher device for use in a digital video transmission system, thedigital video switcher device transmitting digital audiovisual data to adigital video sink over a security protocol link, the output boardcomprising: a receiver adapted to receive the digital audiovisual datafrom at least two input boards; a scaler adapted to convert the receiveddigital audiovisual data to a native resolution of the video sink and togenerate switched digital audiovisual data during a switching eventbetween the at least two input boards, the switched digital audiovisualdata comprising a substantially continuous stream of uninterrupteddigital video timing data, wherein the substantially continuous streamof uninterrupted digital video timing data is generated in the absenceof digital video timing data received from each of the at least twoinput boards; and a transmitter adapted to encrypt and transmit theoutput of the scaler, and is further adapted to maintain the securityprotocol link in an authenticated interface with the digital video sink.13. The output board according to claim 12, wherein the switching eventcomprises: at least one of a switch from receiving audiovisual data froma first source to receiving audiovisual data from a second source, aswitch from receiving audiovisual data at a first resolution toreceiving audiovisual data at a second resolution, and a switch fromreceiving audiovisual data at a first refresh rate to receivingaudiovisual data at a second refresh rate.
 14. The output boardaccording to claim 12, wherein the scaler is adapted to generate imagecontent data during the switching event.
 15. The output board accordingto claim 14, wherein the scaler is adapted to generate image contentdata after a switching event until receiving a sufficient amount ofdigital audiovisual data to generate a stable output of converteddigital audiovisual data.
 16. The output board of claim 12 wherein, thesecurity protocol comprises High-Bandwidth Digital Content Protection(HDCP).
 17. A method for reducing switching delay when switching sourcesin a digital video distribution network, the method comprising:receiving digital audiovisual data at a first input board from a firstdigital video source; receiving digital audiovisual data at a secondinput board from a second digital video source; routing audiovisual datafrom the first input board to an output board; transmitting the digitalaudiovisual data from the output board to a digital video sink;receiving a user control signal to switch from the first digital videosource to the second digital video source; generating a substantiallycontinuous stream of uninterrupted digital video timing data at theoutput board during a delay when switching between digital audiovisualdata from the first input board and digital audiovisual data from thesecond input board, the switching comprising a switching event, whereinthe generated substantially continuous stream of uninterrupted digitalvideo timing data is generated in the absence of digital video timingdata received from either or both of the first input board and thesecond input board during the switching event.
 18. The method accordingto claim 17, further comprising: routing the digital audiovisual datafrom the second input board to the output board; and transmitting thedigital audiovisual data from the output board to the video sink. 19.The method according to claim 17 further comprising: scaling the digitalaudiovisual data received from the first input board to a nativeresolution of the display; and scaling the digital audiovisual datareceived from the second input board to the native resolution of thedisplay.
 20. The method according to claim 17 further comprising:generating image content data during the switching event.
 21. The methodaccording to claim 21 further comprising: continuing to generate digitalaudiovisual data at the output board until an amount of digitalaudiovisual data sufficient to produce stable scaled digital audiovisualdata is received from the second input board.
 22. The method accordingto claim 17 further comprising: transmitting a prepare signal to theoutput board.
 23. The method according to claim 17, wherein the step ofgenerating a continuous stream of uninterrupted video timing datacomprises: automatically generating video timing data in a free funningmode at the output board.